1. Field of the Invention
The present invention relates to an X-ray switching and generating device which switches and generates X-rays for diagnosis and curing.
2. Description of the Related Art
X-rays are electromagnetic waves having a wavelength of about 0.1 to 100 A (10−11 to 10−8 m). Among the ray, an X-ray having a short wavelength (10 to 100 keV, λ=1 to 0.1 A) is referred to as a hard X-ray, and an X-ray having a long wavelength (0.1 to 10 keV, λ=100 to 1 A) is referred to as a soft X-ray. Moreover, an X-ray emitted at a time when an electron beam or the like is struck on a substance and having a wavelength inherent in a constituting element of the substance is referred to as a particular X-ray.
As apparatuses in which the X-rays are used, an X-ray transmission apparatus, an X-ray CT apparatus, an X-ray diffraction apparatus, an X-ray spectral apparatus and the like are utilized in broad fields such as a medical treatment, bioscience and material science. For example, to cure cardiac infarction, coronary angiography (IVCAG) in which an X-ray of about 50 keV is used is generally performed. Moreover, the X-ray CT apparatus is an apparatus in which an object to be measured is irradiated with X-rays from different directions to measure absorption of the rays, and an image is reconstructed by a computer to obtain a two-dimensional sectional image of the object.
As generation sources of the X-rays, an X-ray tube and synchrotron radiation light are known.
The X-ray tube is a device in which a thermion obtained by heating a filament in vacuum is accelerated at a high voltage, and is allowed to collide with a metal anode (target), thereby generating the X-ray. Examples of the X-ray to be generated from the X-ray tube include a continuous X-ray obtained by braking radiation of an electron, and a particular X-ray which is a bright line spectrum. The continuous X-ray is used as a light source for an application in which any X-ray having a specific wavelength is not required, for example, a transmission process for a medical treatment or industry. The particular X-ray is used for an application in which the X-ray having the specific wavelength is required, for example, X-ray diffraction, fluorescent X-ray spectroscopy or the like.
On the other hand, the synchrotron radiation light (SR light) is an X-ray generated during an orbit change in a case where an orbit of the electron beam accelerated at a speed close to a light speed is changed by a strong magnet in an annular accelerator (a synchrotron). The SR light is an X-ray source (e.g., an X-ray intensity (a photon number): about 1014 photons/s, a pulse width: about 100 ps) which is incommensurably intense as compared with the X-ray tube, and the light is used for a field in which a high X-ray intensity is required.
However, a synchrotron radiation light facility in which a synchrotron is used is a large-sized facility in which the synchrotron has a large diameter of about 50 m or more, and an orbit length reaches 100 m or more. Therefore, there is a problem that the facility even for a research or the medical treatment cannot easily be introduced. To solve the problem, a small-sized X-ray generation device is proposed in which a small-sized linear accelerator is used (e.g., Non-Patent Document 1).
On the other hand, in a conventional X-ray CT apparatus, a monochromatic meter including two crystal plates is used as means for obtaining a monochromatic hard X-ray from the radiation light. Since the monochromatic X-ray CT apparatus has a low measurement precision of an electron density, a mixed two-color X-ray CT apparatus is proposed in which two types of X-rays having different mixture ratios of a dominant wave and a higher harmonic wave are used (e.g., Non-Patent Document 2).
Moreover, Patent Document 1 has already been disclosed as a diagnosis and curing apparatus in which the particular X-ray is used as the X-ray for irradiation, and Patent Document 2 has already been disclosed as a diagnosis and curing apparatus in which the electron beam is used for curing and the X-ray is used for diagnosis.
In “Small-Sized X-Ray Generation Device” of Non-Patent Document 1, as shown in FIG. 1, an electron beam 52 accelerated by a small-sized accelerator 51 (an X-band acceleration tube) is allowed to collide with laser 53 to generate an X-ray 54. The multi-bunch electron beam 52 generated by an RF electron gun 55 (a thermal RF gun) is accelerated by the X-band acceleration tube 51, and collides with the pulse laser light 53. The hard X-ray 54 having a time width of 10 ns is generated by Compton scattering.
This device is miniaturized by using an X-band (11.424 GHz) corresponding to a frequency four times as high as that of an S-band (2.856 GHz) for general use in a linear accelerator as an RF for acceleration of the electron beam. For example, it is predicted that the hard X-ray having an X-ray intensity (the photon number) of about 1×109 photons/s and a pulse width of about 10 ps is generated.
As shown in FIG. 2, “Mixed Two-Color X-Ray CT Apparatus” of Non-Patent Document 2 includes a rotary filter 61, a monochromatic meter 62, a collimator 63, a transmission type ion chamber 64, a scattering member 65, a sliding rotary table 66, an NaI detector 67 and a plastic scintillation counter 68. A dominant wave X-ray of 40 keV and a double higher harmonic wave X-ray of 80 keV are extracted from synchrotron radiation light 69a by the monochromatic meter 62, a mixture ratio of the 40 keV X-ray and 80 keV X-ray is regulated by the rotary filter 61, scattered X-ray spectrum from the scattering member 65 is observed by the NaI detector 67 to measure the mixture ratio, a size of a mixed two-color X-ray 69b is adjusted by the collimator 63, and the ray is transmitted through the transmission type ion chamber 64 and a subject 60. An intensity of the ray is measured by the plastic scintillation counter 68.
According to this apparatus, the measurement precision of the electron density is improved. Moreover, the apparatus is successful in preparation of an image of the electron density and an effective atomic number.
As shown in FIG. 3, “X-Ray Diagnosis Apparatus and X-Ray Curing Apparatus” of Patent Document 1 is an X-ray diagnosis apparatus in which an X-ray blocking metal complex taken by a person 77 being inspected is selectively accumulated in an affected part of the person, and the part is irradiated with an X-ray from X-ray generation devices 71, 72 to form an X-ray image of the affected part with an X-ray image pickup device 76. A metal target 73 to generate a particular X-ray which belongs to a predetermined energy region is used, and an electron beam generated by the electron generator 71 and accelerated by the electron accelerator 72 is struck on the metal target 73 to generate the particular X-ray. The ray is used as the X-ray for irradiation.
It is to be noted that, in this drawing, reference numeral 74 is a filter device, and 75 is a bed.
Moreover, “Radiotherapy Apparatus having Low Dose Low Order and Portal Imaging X-Ray Source” of Patent Document 2 is an apparatus which is applicable to both of megavolt radiotherapy and diagnosis X-ray source for portal imaging. As shown in FIG. 4, both of an electron beam 81 (a high-energy curing source) emitted from an electron gun (not shown) and accelerated in a waveguide and an X-ray 85 (a low-energy diagnosis source) generated by collision of an electron beam 83 emitted from an electron gun 82 with a movable target 84 are arranged along the physically same line 86 of the apparatus. The apparatus also includes an actuator which moves the movable target 84 in an axial direction. The beams are arranged at positions for curing or diagnosis, if desired. The electron beam 81 is used for the curing, and the X-ray 85 is used for the diagnosis.
[Non-Patent Document 1]
“Development of Small-Sized Hard X-Ray Source using X-band Liniac”, 2002, authored by Katsuhiro DOHASHI, et al.
[Non-Patent Document 2]
“Development of Mixed Two-Color X-Ray CT System” authored by Makoto SASAKI, et al., Medical Physics Vol. 23 Supplement No. 2 April 2003
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2003-38475 titled “X-Ray Diagnosis Apparatus and X-Ray Curing Apparatus”
[Patent Document 2]
Japanese Patent Application Laid-Open No. 8-206103 titled “Radiotherapy Apparatus having Low Dose Low Order and Portal Imaging X-Ray Source”
Since the “monochromatic hard X-ray” having a narrow band and high energy is used in the X-ray for diagnosis, a clear image can be obtained. Moreover, a patient does not have to be uselessly irradiated with radiation.
Moreover, since a ray position of the X-ray for curing is disposed close to a light source of the X-ray for diagnosis, an error of an X-ray irradiation position can be reduced.
Therefore, to perform the diagnosis and the curing with the same apparatus, there has been a strong demand for an X-ray switching and generation device in which the monochromatic hard X-ray as the X-ray for diagnosis and the particular X-ray as the X-ray for curing are switched and generated at the same light source position.
In the diagnosis and curing apparatus of Patent Document 1, the particular X-ray which belongs to the predetermined energy region is used in both of the diagnosis and the curing. However, this particular X-ray has X-ray energy of 40 keV or more, and has a low absorption ratio with respect to a human body, but this ray is not monochromatic (i.e., has a broad band). Therefore, to obtain the clear image, a c-line blocking metal complex needs to be selectively accumulated of the affected part of the person being inspected. The ray has low energy and broad band even as the X-ray for curing. Therefore, the X-ray blocking metal complex needs to be accumulated in the affected part, and there has been a problem that a large burden is imposed on the person being inspected.
Moreover, in the diagnosis and curing apparatus of Patent Document 2, the electron beam is used for the curing, and the X-ray is used for the diagnosis. However, the X-ray is used for diagnosis, the X-ray for curing is required. Therefore, the apparatus becomes complicated and expensive.
To obtain the monochromatic hard X-ray from the radiation light, as disclosed in Non-Patent Document 2, the monochromatic meter including two crystal plates can be used. However, since the radiation light source is a large-sized facility, there is a problem that even for research or medical treatment the light cannot easily be introduced.
Moreover, in a case where two types of X-rays are used in order to improve the precision of the X-ray image during the X-ray diagnosis and measure both of the distributions of the electron density and the effective atomic number, a crystal angle of the monochromatic meter needs to be precisely regulated. Therefore, it is very difficult to switch the rays at a high speed in a short time.
Furthermore, in a case where the mixed two-color X-ray obtained by mixing the dominant wave X-ray and the double higher harmonic wave X-ray are mixed is extracted from the synchrotron radiation light as in Non-Patent Document 2, the wavelength of the X-ray is limited to that of the higher harmonic wave. There is also a problem that the dominant wave cannot be separated from the higher harmonic wave.
The present invention has been developed in order to satisfy the above demands. That is, an object of the present invention is to provide a device for switching/generating X-rays for diagnosis and curing in which a monochromatic hard X-ray as the X-ray for diagnosis and a particular X-ray as the X-ray for diagnosis can be switched and generated in order to perform the diagnosis and the curing with the same apparatus.